[clang] [-Wunsafe-buffer-usage] Allow strerror for %s in printf-like calls (PR #175208)

[Hans Wennborg via cfe-commits]

zmodem wrote:

> do we have an existing optimized "does this string match any of this statically known set of strings?" tool?

Best I can think of is `llvm::StringSet`.

https://github.com/llvm/llvm-project/pull/175208